Exhaust gas muffler with multiple outlet tubes



3,447,630 EXHAUST GAS MUFFLER WITH MULTIPLE OUTLET TUBES Filed Sept. 27,1957 June 3, 1969 c. DAVIDSON FIG-5 INVENTOI? GEORGE L. DAVIDSON June 3,1969 G. vmso 3,447,630

EXHAUST GAS MUFFLER WITH MULTIPLE OUTLET TUBES Filed Sept. 27, 1967Sheet 2 of s l/VVE/VT'OI? GEORGE L. DAVIDSON G. L. DAVIDSON EXHAUST GASMUFFLER W'I TH MULTIPLE OUTLET TUBES Filed S pt. 27. 1967 June 3, 1969 vSheet FIG-.13

M/VEWTOR GEORGE L. DAVIDSON United States Patent US. Cl. 181-60 30Claims ABSTRACT OF THE DISCLOSURE The engine exhaust gas mufilerincludes a plenum, an inlet pipe receptive of engine exhaust gases, anda peculiar arrangement of small exhaust tubes through which gases fromthe plenum are finally released; the exhaust tubes having certaincritical dimensions and arrangements relative to each other and to aninclined mounting plate associated with the plenum. The exhaust tubesare of two kinds, which working together, apparently create in theplenum a pulsing vortex of exhaust gas presumably moving at a suddenaccelerated rate through the small exhaust tubes to produce a negativepressure within the plenum chamber for promptly and noiselesslydispatching the exhaust gases and any other media fed to the mufller.Several dimensional limits as disclosed, as well as criticalrelationships of constituent parts, are of primary importance to theinvention. 1

The present invention relates to an engine exhaust gas mufl'ler, such asmay be employed in controlling the exhaust gases of internal combustionengines of various kinds.

An object of the invention is to provide an improved mufller whichminimizes objectionable noise and backpressure, and the emission of livesparks, from the exhaust gases of an internal combustion engine.

Another object of the invention is to provide an improved mufller of thecharacter stated, which in terms of the desirable objectives realizedthereby, is highly superior in performance to muffiers as heretoforeconstructed.

A further object of the invention is to provide in a mutiler, means of asimple and inexpensive nature for obtaining superior performance and ahigh degree of e'fficiency in the attainment of the objectives abovestated, without sacrificing durability and longevity of service.

Another object of the invention is to provide an acoustical plenum-typemuffler having the desirable characteristics and advantages abovestated, which employs no movable or adjustable parts capableof.producing noise and rattle in the presense of vibration and eventualdeterioration resulting from the corrosive effects of the gasescontrolled, which may include water of condensation rendered corrosiveby the exhaust gases.

A further object is to provide an improved muffler which is effectivefor use in controlling the exhaust gases of all types of internalcombustion engines, including marine engines which exhaust coolant asWell as exhaust gases through the mufiier, and diesel engines whichexhaust scavenger additives with the products of combustion.

The foregoing and other objects are attained by the means describedherein and illustrated upon the accompanying drawings, in which:

FIG. 1 is a side elevational view of the improved muffier, whichincludes a plenum chamber, an inlet pipe, and a plurality of outlettubes.

FIG. 2 is a fragmentary enlarged cross-section transversely through theplenum chamber, and in the direction of the outlet tubes.

FIG. 3 is a view similar to FIG. 2, showing a modification.

FIG. 4 is an enlarged cross-section taken on line 4-4 of FIG. 1.

FIGS. 5 and 6 are side elevational views, partly broken away, andshowing two forms of outlet tubes utilized in the muffler construction.

FIG. 7 is a fragmental side elevation showing a modification of FIG. 1.

FIG. 8 is a view similar to FIG. modification of FIG. 7.

FIG. 9 is a fragmental side elevation similar to FIG. 8, showing theplenum chamber equipped with a lesser number of outlet tubes.

FIG. 10 is an enlarged cross-section taken on line 10-10 of FIG. 9.

FIG. 11 is a view similar to FIG. 10, showing the plenum chamberequipped with a greater number of outlet tubes.

FIG. 12 is a transverse cross-section similar to FIG. 4, and showing theplenum chamber equipped with a single circular row of outlet tubes.

FIG. 13 is a side elevation, partly broken away, showing a mufflersimilar to that of FIG. 1 but modified espe cially for marine engineapplication.

FIG. 14 is a cross-sectional view on an enlarged scale, and taken online 1414 of FIG. 13.

The acoustical muffler as illustrated by all the drawing views, maycomprise an elongate hollow plenum chamber or body 20, preferablycylindrical of shape, and constructed preferably of acorrosion-resistant metal. The plenum chamber or body 20 may be providedwith a front or inlet end closure plate or member 22, and a rear oroutlet end closure plate or member 24, each of which may be peripherallyattached to an open end of body 20 in any suitable manner, as by meansof welding or crimping, to establish the volumetric capacity of theplenum chamber.

The front closure plate 22 may support an inlet pipe 26 through whichexhaust gases from an engine may be introduced into the plenum chamber.The inlet pipe communicates with the plenum chamber through an openingin plate 22, as will be understood.

The rear closure plate 24 is located at the discharge end of the plenumchamber, and is provided with a plurality of openings in which may befixedly supported a series of exhaust outlet tubes which projectgenerally rearwardly from plate 24. The exhaust outlet tubes bear theidentifying characters A and B, and the inside diameter of each thereofis considerably smaller than the inside diameter of inlet pipe 26. Thetubes A and B are open at opposite ends thereof, said open ends beingdesignated 28 and 30. The ends 28 may be referred to as the inner endsof the exhaust tubes, and the ends 30 may be considered the outer endsthereof, due to their inner and outer disposition with respect to theinterior of the plenum chamber.

The principal difference between an exhaust tube A and an exhaust tubeB, is that tube A is provided with a single side aperture 32 (FIG. 6),whereas a tube B (FIG. 5) is provided with a double side-aperture, ortwo sideapertures 34 and 36 whose centers are located substantially atopposite ends of a diameter of tube B, near the open end 28 thereof aswill be explained later in greater detail. The side-apertures are inevery instance disposed within the confines of the plenum chamber, andeach exhaust tube is to be fixed upon plate 24 at a location between itsside-aperture or apertures, and the outer end 30 of the tube. Fixationof the exhaust tubes to plate 24 may be effected in any suitable manner,and by means of welds, for example. The side-apertures are to be lightlychamfered exteriorly of the exhaust tubes.

The major axes of all the tubes A and B preferably 7, showing a slightare substantially parallel to one aonther. In some instances, the majoraxes of the tubes A and B are parallel to the major axis of the plenumchamber, as in FIGS. 1 and 13, whereas in other instances the major axisof the tubes A and B may be inclined to the major axis of the plenumchamber, as in FIGS. 7, 8 and 9. The tubes A and B may be of equallength.

Several critical considerations are to be observed in fabricating andassembling the constituent parts of the mufller in order to achieve thedesired maximum reduction of noise level, back-pressure, andspark-arresting performance. It has been determined, for example, thatinclination of the rear closure plate with respect to a plane normal tothe plenum chamber axis, must approximate 12 (twelve) degrees, and maynot depart from the twelve degree inclination more than 2 (two) degreesin either direction. Thus it will be understood that inclination of therear closure plate with respect to a plane normal to the plenum chamberaxis, must be between and 14 degrees. The rear closure plate is to besubstantially flat, or planar, where exposed to the interior of theplenum chamber.

Another critical consideration resides in the selection of tubes such asA and B, and their relationship to the inner surfaces of rear closureplate 24 and the inner wall of the plenum chamber. Considering FIGS. 1,3 and 4, and particularly FIG. 4, it will be noted that the rear closureplate or member 24 supports an outer circular row of tubes A and B, andan inner circular row of such tubes. The tubes A and B of the outercircular row, of which there are fifteen shown by Way of example (butnot of necessity), are arranged so that in the main, tubes A arealternated with tube B in the circular row, but the number of tubes B(the double-apertured tubes), exceeds the number of signal-aperturedtubes A in the same row. In the FIG. 4 example, the number of B-tubesexceeds by one, the number of A-tubes employed; however, it must beunderstood that the excess of B-tubes must be more than one with amaximum of two.

The inner circular row of tubes A and B in the FIG. 4 example, compriseseight tubes mainly alternated, though not strictly so, since the numberof B-tubes exceeds by two the number of A-tubes employed. Here, as inthe outer circular row of tubes, the double-apertured tubes B mustexceed in number the number of singleapertured tubes A if the bestmufiie performance is to be obtained.

It is imperative that the tubes of the outermost circular row be spacedfrom one another, and from the inner cylindrical surface of the plenumchamber 20, a distance not less than one-fourth inch, this being aprerequisite whether or not the structure includes an inner circular rowof tubes, which may be omitted as in FIGS. 10, 11 and 12. Regardless ofthe number of tubes employed in the outer circular row, the tubes of therow require a spacing of not less than one-fourth inch from the closestpoint on the inner surface of the plenum chamber wall.

With reference again to FIGS. 3 and 4, attention is directed to theillustrated angular disposition of the side apertures 32, 34 and 36,with respect to radii of the plenum chamber passing through each exhausttube axis. Considering tube A of FIG. 3, it is seen that the centerlineof side aperture 32 has a required angularity of to 30, to a chord Cwhich bisects tube A and meets radius R at right angles on the tubeaxis. The 20 to 30 angle mentioned is denoted L in FIG. 3, and indicatesa clockwise rotation of tube aperture 32 from the line of chord C, sothat the aperture center-line meets the inner cylindrical wall of plenumchamber 20 at an acute angle.

Tube B of FIG. 3 likewise is turned in clock-wise direction, to disposethe center-line of aperture 34 at an angle L to chord C, said angle Lbeing of a value between 20 and 30. Chord C bisects tube B and meetsradius R at right angles on the axis of tube B. The center-line ofsideaperture 34 of tube B meets the inner cylindrical wall of chamber 20at an acute angle which corresponds to the angle at which said wall isintersected by the side-aperture 32. Thus, the center-lines ofside-apertures 32 and 34 of tubes A and B, project obliquely outwardlyin a generally common direction within the plenum chamber. Theside-aperture 36 of tube B, however, faces in an opposite direction, andis farther distant from the chamber wall than is aperture 34.

All of the exhaust tubes in the outer circular row of FIG. 4 are seen tobear the above-described orientation to the plenum chamber cylindricalwall, and to one another, as an important factor in the construction ofthe improved mufiler. The mufller may be constructed either with orwithout the inner circular row of exhaust tubes, and if the inner row isincorporated in the construction, the'sideaapertures of the inner row oftubes are to be angled according to the teaching recited in the nextpreceding paragraph. That is, each one of the tubes of the inner rowwill have its center located upon a radius of the plenum chamber, andwill be rotated in clockwise direction to dispose a side-aperturecenter-line at an angle of 20 to 30 to a chord which bisects the tubeand meets the chamber radius at right angles on the tube axis. Thus,corresponding side-apertures of the tubes A and B constituting the innercircular row of tubes, will have their center-lines projected in thesame general direction as those of the outermost circular row of tubes.

The aforesaid angular disposition of the tube sideapertures, incombination with the unequal porting resulting from utilizing a greaternumber of B-type tubes than A-type tubes in the muffler construction, isbelieved to create a highly beneficial vortex pattern of gases withinthe plenum chamber as the gases pass therethrough. Also, for bestperformance, it has been determined that exhaust tubes A and B mustproject into the plenum chamber at least one inch, and the diameter ofthe side apertures 32, 34, 36, must closely approximate one-half theinside diameter of the exhaust tube. The inside diameter of tubes A andB must not exceed .750 inch; if larger tubes are used, a substantialloss of control of the exhaust gases will ensue. An exhaust tube insidediameter ranging between .750 and .350 inch, is considered preferable,and as above stated, the diameter of the side-aperture or aperturesshall closely approximate one-half the inside diameter of the exhausttube in all cases.

The length of each exhaust tube may approximate 7 or 8 inches, inmufilers designed for use with engines of the sizes ordinarily appliedto passenger automobiles. A 20 percent increase or decrease in thelength specified may be expected to produce no unfavorable results.

In the description of FIGS. 1, 3 and 4, reference was made to anassembly procedure wherein all of the exhaust tubes A and B were fixedafter being rotated in a clockwise direction, by an amount rangingbetween 20 and 30 from a starting position at which the center-lines ofthe side-apertures coincided with a chord such as C or C. An alternativeassembly, equally effective, is to rotate the exhaust tubescounter-clockwise, by the same amount. The effect of the alternativeprocedure is merely to reverse the direction of the vortex pattern ofgases within the plenum chamber as the gases pass therethrough. Suchalternative procedure is suggested by FIGS. 2, 10, 11, 12 and 14 of thedrawings.

In FIGS. 2, 10, 11, 12 and 14, and with particular reference to theenlarged view of FIG. 2, it is apparent that tube A has been rotatedcounter-clockwise from a starting position at which the center-line 40of side-aperture 32 coincided with chord C. The resultant angle L mayrange between 20 and 30. Similarly, it is apparent that tube B has beenrotated counter-clockwise to form an angle L between the chord C and thecenter-line 42 of side-aperture 34, the angle L measuring not more than30 nor less than 20. The tubes A and B are to be spaced from oneanother, and from the inside surface of the plenum chamber wall, 'adistance not less than one-fourth inch. The chords C and C pass,respectively, through the axes of tubes A and B, and meet the radii Rand R at right angles. The lines 37 and 39 represent tangents which areparallel to chords C and C.

The above-described disposition of the tube side-apertures is tobeobserved, whether the mufller construction embodies a single circularrow of tubes as in FIGS. 2, 10, 11, 12 and 14, or a double circular rowof tubes as in FIG. 4. It is important that all tubes of a given mufflerbe rotated in one direction only, either clockwise, or counterclockwise;and the number of B-tubes employed must exceed the number of A-tubes aspreviously explained.

The total number of exhaust tubes incorporated in a muffler depends uponthe engine displacement, and the amount of exhaust gas back-pressure atwhich the engine is designed to operate. In general, the totalcross-sectional area of all the exhaust tubes, measured interiorly ofthe tubes, will be somewhat less than the input area of the enginesexhaust manifold. The number of exhaust tubes employed, therefore, willbe dependent upon the engine characteristics.

The inside diameter of the plenum chamber has been found to bear apeculiar relationship to the length of the plenum chamber. The optimumfor masking sound on all db scales of A, B, C, appears always to fall inthe 2.5 :1 area. It is therefore desirable that the length of the plenumchamber be 2.5 times the diameter; however, if a deeper pitch of soundis desired, the ratio of 2.5:1 may be altered in a direction approachingunity, or 1:1. Altering the ratio in the opposite direction will producea higher pitch of sound.

The mufiler construction of FIG. 8 differs from that of FIG. 1, in thatthe exhaust tubes of FIG. 8 are fixed to rear plate 24 at right anglesto the plane of said plate,

Whereas in FIG. 1 the exhaust tubes project angularly from the plane ofthe rear plate. Otherwise stated, the exhaust tubes of FIG. 8 areinclined to the major axis of the plenum chamber, whereas in FIG. 1 theexhaust tubes have their major axes disposed in substantial parallelismwith the major axis of the plenum chamber. In either case, however, theinclination of the end plate to a perpendicular line on the plenumchamber axis, is to be 12 degrees, plus or minus 2 degrees, aspreviously pointed out herein.

In the FIG. 7 modification, the inclined rear end plate 24 may beconsidered a baffle plate separate and apart from a true end closureplate 24' through which the exhaust tubes pass also. The exhaust tubesmay be welded or otherwise fixed to closure plate 24, which in turn iswelded or otherwise fixed to the plenum. end. If desired, the tubes maypass through individual tube-supporting openings in plate 24, withoutbeing welded thereto. However, plate 24 is to be appropriately supportedwithin the plenum chamber at the aforesaid inclination of 12 degrees,plus or minus 2 degrees, with reference to a perpendicular lineintersecting the major axis of the plenum chamber. The inner ends 28 ofthe exhaust tubes are to extend beyond plate or baflie 24 and into theplenum chamber a distance of at least one inch. Thus, the sideaperturesof all the exhaust tubes will be located within the main chamber of theplenum.

As in all other forms of the muflier disclosed, the modifications ofFIGS. 7 and 8 require a greater number of B-type tubes than A-typetubes, and the side-apertures thereof must be angles in accordance withthe teaching of either FIG. 2 or FIG. 3, as previously explained indetail herein.

The side-apertures of all tubes A and B are to be of a diameter closelyapproximating one-half the inside diameter of a tube, and thecenter-line of each side-aperture is to be distant from the inner end 28of the tube by the amount of one-half inch. Projection of the inner ends28 of the tubes A and B into the plenum chamber, may be one inch orslightly more, but not less than one inch.

As was previously pointed out herein, any of the mufiler forms hereindisclosed is suitable for marine engine use, as well as for use withengines that do not exhaust water or coolant through the exhaust systemthereof. FIGS. 13 and 14, however, illustrate a mufiler constructionwhich is especially adapted for marine engine use. It employs the samesystem of A and B type exhaust tubes, constructed and arranged inaccordance with the teaching hereinbefore disclosed, but with the B-typetubes in much greater predominance over the A-type tubes.

In accordance with FIGS. 13 and 14, there is provided an elongate ductor channel member 46 of rigid material, such as metal for example,having its legs 48 and 50 welded or otherwise fixed to the inside of theplenum, with the channel member inverted to provide a passageway 52. Thechannel member may extend from the approximate location of front closureplate 22, rearwardly to and through rear closure plate 24, with its openbottom. exposed beyond the plenum at 54 from rear plate 24 to the outerterminal end '56. The channel member may be straight as shown, anddisposed in substantial parallelism with the major axis of the plenumchamber.

The upright legs 48 and 50 may be apertured at several locations withinthe confines of the plenum chamber, to provide a multiplicity of ports58 into which coolant water from the engine jacket may enter, to bedischarged at the open bottom '54 and the open end 56 of the channelmember. When the marine engine is in operation, the coolant water andexhaust gases will enter the plenum chamber through inlet pipe 26, andthe major portion of the water, if not all of it, will gravitate intothe duct or passageway 52 for expulsion from the muffler at 54 and 56.The gaseous portion of the exhaust from the engine will enter theexhaust tubes A and B, possibly along with some of the water at times,for expulsion through the open rear ends 30 of the tubes.

The gaseous exhaust in passing through the plenum chamber and tubes Aand B, will by the action of said tubes become a pulsing vortex of gas,apparently moving at a sudden accelerated rate through the severalexhaust tubes. This accelerated rate of gas movement, so far as can bedetermined, apparently functions somewhat as a negative pressuregenerator within the plenum chamber and has shown unusual capability toassist in discharging the water portion of the engine exhaust, as wellas the gaseous portion thereof. The same reaction appears to occur inthe muffiing of diesel engine exhaust gas, wherein may be present invarying degrees, scavenger or blower air additives which must bedischarged through the mufiier with dispatch in the interests of engineefi'iciency and fuel conservation. The same reaction appears to occur inthe mufliing of gasoline-fueled engine exhaust gases, with greatefliciency resulting along with quiet operation.

In cases of diesel as well as marine engine application, optimum resultshave been obtained when the plenum chamber capacity is equal to, orwithin plus or minus 5 percent of the engine displacement.

In conclusion, it is necessary to consider that no definitely reliabletheoretical basis has evolved from the many tests and experiments thathave been conducted in bringing the present invention to fruition. It isknown, however, that certain of the arrangements and critical dimensionsdisclosed herein, and the limits within which such dimensions may bevaried, must be observed if the device of the invention is to performthe high degree of effectiveness of which the device is capable.

It is to be understood, however, that various modifications and changesof a non-critical nature may be made in the device without departingfrom the spirit of the invention.

What is claimed is:

1. An exhaust mufiler for internal combustion engines, comprising:

(a) a substantially cylindrical plenum chamber including an outer wall,an inlet end and an outlet end wherein the outlet end is inclined 10 to14 from a plane normal to the longitudinal axis of the chamber;

(b) a plurality of elongate cylindrical exhaust tubes projecting throughsaid outlet end, said tubes each having an inner open end and an outeropen end, with an inner end of each exhaust tube extending at least oneinch into the plenum chamber;

(c) certain of said exhaust tubes having a single transverseside-aperture through that portion of the tube wall disposed inside theplenum chamber;

(d) other of said exhaust tubes having a pair of transversediametrically aligned side-apertures through that portion of the tubewall disposed in the plenum chamber, and

(e) wherein the number of exhaust tubes having a pair of side-aperturesexceeds the number of exhaust tubes having a single side-aperture.

2. An exhaust mufiler as described in claim 1, wherein the axes of theside-apertures in the exhaust tube walls pass through the major axis ofeach respective tube, with the axes of said apertures of all of thetubes being inclined to 30 either counterclockwise or clockwise relativeto a reference line passing through the center of each tube and standingperpendicularly upon a plenum radius passing through the center of eachrespective tube.

3. An exhaust mufiler as described in claim 2, wherein the side-apertureof each exhaust tube having a single aperture faces toward a point onthe wall of the plenum, which point is located between adjacent exhausttubes.

4. An exhaust muffler as described in claim 3, wherein the diameter ofthe respective side-apertures through the Walls of the exhaust tubes areone-half the inside diameter of said tubes.

5. An exhaust mufiier as described in claim 4, wherein the center-lineof said side-apertures in the walls of the exhaust tubes are one-halfinch from the inner open ends thereof.

6. An exhaust muffler as described in claim 1, wherein the ratio of thelength to internal diameter of the plenum chamber is 2 /2 to 1.

7. An exhaust muffier as described in claim 1, wherein the combined areaof the exhaust tubes is less than the inlet area to the plenum chamber.

8. An exhaustrnufiier as described in claim 1, wherein there are twoless exhaust tubes having a single aperture than exhaust tubes having apair of apertures.

9. An exhaust muffler as described in claim 1 wherein the outer wall ofan exhaust tube is at least A inch from the inner surface of the outerwall of the plenum chamber.

10. An exhaust muffler as described by claim 1, wherein the exhausttubes are substantially parallel to one another, and are arranged uponthe plenum chamber outlet end in circular row formation, characterizedby substantial alternation of the exhaust tubes having a Singleside-aperture, with those exhaust tubes having a pair of side-apertures.

11. An exhaust muffler as described by claim 10, wherein theside-apertures of all the exhaust tubes are of a diameter approximatingone-half the inside diameter of the tubes in which the apertures areformed, and wherein the axes of the side-apertures in the exhaust tubewalls pass through the major axis of each respective tube, with the axesof said apertures of all the tubes being inclined 20 to 30 eitherclockwise or counter-clockwise relative to a reference line passingthrough the axis of each tube and standing perpendicularly upon a plenumchamber radius which passes through the center-line of each respectivetube.

12. An exhaust mufller as described by claim 11, wherein the axes of allthe side-apertures are spaced one-half inch from the inner ends of theirrespective exhaust tubes, and the diameter of any such side-aperturedoes not exceed .750 inch.

13. An exhaust muffler as described by claim 12, wherein the spacingbetween adjacent exhaust tubes, and the spacing of each exhaust tubefrom the plenum chamber wall, is no less than one-fourth inch.

14. An exhaust mufiler as described by claim 13, wherein the open innerends of the exhaust tubes project into the plenum chamber at least oneinch.

15. An exhaust mufiler as described by claim 11, wherein the inner endsof the exhaust tubes project into the plenum chamber at least one inch.

16. An exhaust muffier as described by claim 14, where in the ratio oflength to internal diameter of the plenum chamber approximates 2 /2 :1.

17. An exhaust mufller as described by claim 1, wherein theside-apertures of the exhaust tubes are chamfered at the exteriorsurface of said tubes.

18. An exhaust mufller as described by claim 2, wherein the combinationincludes: an inverted elongate channel member having spacedsubstantially parallel legs edgewise abutting the inner surface of theplenum wall to form therewith an elongate passageway, said channelmember at one end extending exteriorly of the plenum through the outletend of the latter to convey exhaust from the chamber of the plenum, saidchannel member being apertured interiorly of the plenum chamber toprovide for fluid communication between the plenum chamber and thechannel member passageway.

19. An exhaust muffler as described by claim 18, wherein the aperturesof the channel member are formed in the legs thereof, and the exteriorlyextended end of the channel member passageway is open for unrestricteddischarge of exhaust leaving the plenum chamber.

20. An exhaust mufiler for internal combustion engines, comprising incombination:

(a) an elongate plenum including an outer wall, an

apertured inlet end wall, and a multiple-apertured outlet end well, saidwalls defining a plenum chamber for exhaust media;

(b) said outlet end wall being substantially planar, and inclined 10 to14 from a plane normal to the longitudinal axis of the plenum chamber;

(c) a plurality of elongate cylindrical open-end exhaust tubesprojecting each though an aperture of the outlet end wall, with one endof each tube exposed exteriorly of the plenum chamber, and the remainingend of each tube disposed within said chamber;

(d) and means including said exhaust tubes, for creating within theplenum chamber a pulsing vortex of exhaust media introduced through theaperture of the plenum inlet wall and leaving the plenum chamber throughsaid exhaust tubes.

'21. An exhaust muffler as described by claim 20, Wherein the means lastmentioned includes tnansverse sideapertures formed in the exhaust tubesnear those ends of the tubes which are disposed within the plenumchamber; some of said side apertures being directed toward the innersurface of the plenum outer wall at an angle of between 20 and 30 to aperpendicular line which intersects a second line projected outwardlyfrom the center of the plenum chamber and through the major axis of atube, said angles having their apieces projected toward the includedangle located at the next adjacent tube.

22. An exhaust muffler as described by claim 21, wherein the exhausttubes are arranged in a circular row upon the outlet end wall of theplenum, and wherein more than half of said tubes are provided each witha second side-aperture diametrically aligned with the firstmentionedaperture, most of the tubes which have but one aperture being alternatedwith tubes having two apertures, in forming the circular row of tubes.

23. An exhaust mufller as described by claim 22, wherein the exhausttubes are of equal inside diameters, and the side-apertures thereof areof a diameter equal to one-half the inside diameter of a tube; saidside-apertures being located with their centers spaced one-half inchfrom the interior end of a tube, and said interior end being projectedinto the plenum chamber at least one inch.

24. An exhaust mufiler as described by claim 23, wherein the exhausttubes of the circular row of tubes are spaced from one another, and fromthe inner surface of the plenum outer wall, a distance of at leastone-fourth inch; and wherein the side-apertures of the exhaust tubes arechamfered at the exterior surface of said tubes.

25. An exhaust mufiler as described by claim 24, wherein the ratio oflength to internal diameter of the plenum chamber approximates 2 /2 :1.

26. An exhaust muffler as described by claim 24, wherein the totalinside transverse area of all the exhaust tubes is less than the area ofthe plenum inlet wall aperture.

27. An exhaust muflier as described by claim 24, wherein the combinationincludes: an inverted elongate channel member having spacedsubstantially parallel legs edgewise abutting the inner surface of theplenum outer wall to form therewith an elongate passageway, said channelmember having one end extended exteriorly of the plenum through theoutlet end wall thereof, to convey exhaust media from the chamber of theplenum, said channel member being apertured within the plenum chamber toprovide for fluid lcommunication between the plenum chamber and saidpassageway.

28. The exhaust mufiler as described by claim 27, wherein the aperturesof the channel member are formed in the legs thereof.

29. The exhaust mufiier as described by claim 28, wherein the exteriorlyextended end of the channel member passageway is open for unrestricteddischarge of exhaust media leaving the plenum chamber.

30. The exhaust mufiler as described by claim 29, wherein the combinedtransverse area of the channel member and all the exhaust tubes, is lessthan the area of the plenum inlet wall aperture.

References Cited UNITED STATES PATENTS 1,903,803 4/1933 Barker.2,996,139 8/1961 Patterson 18l-60 XR FOREIGN PATENTS 258 1913 GreatBritain. 577,420 5/ 1958 Italy.

ROBERT S. WARD, JR., Primary Examiner.

US. Cl. X.R. 181-72

